Cooling fan, in particular for motor vehicles

ABSTRACT

A radiator blower, in particular for motor vehicles, is indicated that comprises a plurality of individual fans ( 11, 12 ), each having an electrical drive motor ( 13, 14 ), and a plurality of switches (S 1,  S 2,  S 3 ), each capable of being switched over into two positions, by means of which the drive motors ( 13, 14 ) are capable of being turned on and back off individually or in a series or parallel connection. To prevent disturbing noises from developing when the individual fan ( 11, 12 ) comes to rest after being turned off, when the operating drive motor or motors ( 13, 14 ) is/are turned off, an electronic control unit ( 20 ) forces the switches (S 1,  S 2,  S 3 )—at least temporarily—over into switch positions that bring about a short-circuiting of the turned-off drive motor or motors (FIG.  1 ).

BACKGROUND OF THE INVENTION

[0001] The invention is based on a radiator blower, in particular formotor vehicles, according to the preamble of claim 1.

[0002] Radiator blowers are used in motor vehicles that comprise atleast two separate individual fans to cover a large demand for cooling,which said fans are operated either to ventilate the radiator of theinternal combustion engine evenly, or to ventilate the radiator of theinternal combustion engine and an air conditioner separately within acommon circuit configuration that makes it possible to turn on eitherjust one of the individual fans or both individual fans in series or inparallel.

[0003] When such radiator blowers come to rest after being turned off,they generate noise that is not inconsiderable, because the individualfans pass through various resonant frequencies that, depending onexcitation, can result in disturbing tonal magnifications in the noisespectrum. The tonal magnifications are perceived as being veryunpleasant in particular when an internal combustion engine is runningat idle and producing little noise, or when the internal combustionengine is switched off.

ADVANTAGES OF THE INVENTION

[0004] The radiator blower according to the invention having thefeatures of claim 1 has the advantage that, when the individual fans areswitched off, their drive motors are operated at least temporarily inshort circuit immediately after they are switched off, so that theshort-circuited drive motor operates in the generating mode and comes toa stop after less than 20-30% of its usual slow-down time. The onlyswitches and electric lines used to short circuit the drive motors arethose that are provided in the circuit configuration anyway to performon/off switching functions and establish series and parallelconnections. No additional components are required, therefore, to shortcircuit the drive motors after they are turned off, and noise abatementis achieved at practically no additional cost. The only modificationthat is required is the triggering of the switches-which is carried outas programmed by the electronic control unit-when the individual fansare shut off, which can be achieved by making a cost-negligible softwarechange.

[0005] Advantageous further developments and improvements of theradiator blower indicated in claim 1 are made possible by the measureslisted in the further claims.

[0006] According to a preferred exemplary embodiment of the invention, navailable drive motors are situated in n parallel sub-circuits, wherebyn is a whole number greater than one. The network formed by the nparallel sub-circuits is connected via a switch—designed as a NO contacthaving one active switch contact—to a voltage source. Additionally, tooperate n drive motors individually in n−1 parallel sub-circuits, oneswitch—designed as a NC contact having one active switch contact-isconnected in series with each respective drive motor. These circuitryfeatures make it possible to turn selected drive motors on and off byclosing and opening the NO contact, while the drive motors to be putinto operation are selected by actuating the NC contact. If a NC contactin a parallel branch is opened, the associated drive motor is no longeraffected by the common control by the NO contact.

[0007] To connect the n drive motors in series, according to anadvantageous exemplary embodiment of the invention, a switch designed asa changeover switch having two active switch contacts is located in eachof n−1 parallel sub-circuits. In each case, the changeover contact islocated on the connection side of the drive motor opposite the NCcontact, whereby the first switch contact of the changeover contact islocated in the sub-circuit, and the second switch contact is connectedto the connection between the NC contact and the drive motor in theadjacent sub-circuit. Only one changeover contact is located in thefirst of n parallel sub-circuits, and only one NC contact is located inthe last of the parallel sub-circuits, whereby one is located on thehigh-potential side, and the other is located on the low-potential sideof the respective associated drive motor. This circuit configurationprovides advantages in terms of regulating the speed of the individualfans and adjusting the cooling output.

[0008] Since it is usually sufficient to operate two individual fans inseries, a switch—designed as a changeover contact having two activeswitch contacts—is located, according to an advantageous exemplaryembodiment of the invention, on the connection side of the drive motoropposite the NC contact in each uneven-numbered, parallel sub-circuit ascounted from the NO contact, in order to connect two of the n drivemotors in series, with the possibility of operating the seriesconnections of two drive motors in parallel. The first switch contact ofsaid switch is located in the sub-circuit, and the second switch contactof said switch is connected to the connection between the NC contact andthe drive motor in the subsequent, even-numbered, parallel sub-circuit.A cost advantage can be obtained with this circuit configuration by thefact that a changeover contact can be eliminated from every secondsub-circuit.

[0009] The changeover contacts serving to establish either a series orparallel connection of the drive motors are also used, according to anadvantageous exemplary embodiment of the invention, to temporarily shortcircuit the drive motor that is located in the same parallel sub-circuitby establishing a short-circuit connection in the adjacent, parallelsub-circuit by changing over to the second switch contact via thechangeover contact and the NC contact situated in the closed position.When the NO contact is opened in order to turn the drive motors off, thedrive motor located in the last parallel sub-circuit and connected onlyin series with the NC contact is short-circuited—after at least one ofthe changeover contacts is switched back to its first switch contact—viathe drive motor connected in series with this changeover contact and theclosed NC contact connected in series with said changeover contact inthe sub-circuit.

[0010] According to an advantageous exemplary embodiment of theinvention, an electronic control unit is provided that triggers theswitches—according to a specified program—to change over in order toturn the drive motors on and off and establish the series and parallelconnection. When the drive motors are turned off, the switches aretriggered in such a fashion that the NO contact assumes its openedposition, the NC contacts assume their closed position, and thechangeover contacts are switched over to their first switch contacts. Toturn off the drive motors that are operating, the switches are triggeredin such a fashion that the NO contact opens, the NC contacts are movedto their closed position, and the changeover contacts are temporarilyswitched over to their second switch contact.

SUMMARY OF THE DRAWINGS

[0011] The invention is described in greater detail in the descriptionhereinbelow with reference to the exemplary embodiments presented in thedrawings.

[0012]FIG. 1 is a diagram of a radiator blower having two individualfans operated in one circuit configuration,

[0013]FIG. 2 is a representation of the control program for triggeringthe switches in the circuit configuration according to FIG. 1,

[0014]FIG. 3 is a modified diagram of a radiator blower having twoindividual fans,

[0015]FIG. 4 is a diagram of a radiator blower having three individualfans,

[0016]FIG. 5 is a diagram of a radiator blower having four individualfans.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The radiator blower shown in diagram form in FIGS. 1 and 3comprises two individual fans 11, 12, each of which has a fan wheel 15and 16 driven by an electric drive motor 13 and 14. The drive motors 13,14—designed as DC motors—are integrated in a circuit configuration 10comprising a plurality of switches in such a fashion that they arecapable of being connected to and disconnected from a voltage source 17by actuating the switches accordingly, whereby the two drive motors 13,14 can be operated individually or together in a series or parallelconnection. The switches are switched by an electronic control unit 20that sends appropriate control signals to the switches, according to aspecified program, to reverse them.

[0018] In FIG. 1, the circuit configuration 10 for the two drive motors13, 14 comprises a total of three switches, one of which is designed asa NO contact S1 having one active switch contact, another one of whichis designed as a NC contact S3 having one active switch contact, and thefurther one of which is designed as a changeover contact S2 having twoactive switch contacts. Each switch has two switch positions, 0 and 1,whereby the three switches S1-S3 are designed so that, in thenon-triggered state, they assume their “0” switch position in which theNO contact S1 is open, the NC contact S3 is closed, and the changeovercontact S2 is switched to the first of two active switch contacts.

[0019] The two drive motors 13, 14 are located in two parallelsub-circuits 18 and 19 that are both connected to the voltage source 17via NO contact S1. In sub-circuit 19, NC contact S3 is connected inseries with drive motor 14, while, in sub-circuit 18, changeover switchS2 is connected in series with drive motor 13. The first switch contactof changeover contact S2 is located in sub-circuit 18, so that, whenchangeover switch S2 is switched to the first switch contact (switchposition 0), sub-circuit 18 is closed. The second active switch contactof changeover contact S2 is connected to the connection between NCcontact S3 and drive motor 14 in sub-circuit 19. Changeover contact S2is located in sub-circuit 18 on the low-potential side of drive motor13, i.e., on the ground side, while NC contact S3 in sub-circuit 19 islocated on the high-potential side of drive motor 13. When NO contact S1is closed, therefore, said drive motor is connected with the DC voltagepotential UBat of voltage source 17.

[0020] It is possible to flip-flop the arrangement of the switches S2and S3 with regard for the drive motors 13 and 14 in the parallelsub-circuits 18,19, so that—as shown in the modified circuitconfiguration in FIG. 3—changeover switch S2 is located on thehigh-potential side of drive motor 13, and NC contact S3 is located onthe low-potential side of drive motor 14.

[0021] Switches S1, S2 and S3 are triggered by means of the electroniccontrol unit 20 according to the control program shown in FIG. 2 intable form. Using a control logic integrated in the electronic controlunit 20 and based on operating data, a decision is made whether to putjust drive motor 13 or just drive motor 14 into operation, or to putboth drive motors 13,14 in operation in a parallel or series connection.

[0022] When the radiator blower is turned off, all switches S1, S2 andS3 assume their “0” switch position, as illustrated in FIG. 1.Basically, NO contact S1 serves to establish the electrical connectionwith the voltage source 17. NC contact S3 and changeover contact S2determine whether individual fan 11 or individual fan 12 is put intooperation, or whether both fans 11 and 12 are put into operation in aseries or a parallel connection.

[0023] If the intention is to turn on only individual fan 11 with drivemotor 13, then the electronic control unit 20 closes NO contact S1 andopens NC contact S3, as indicated in the first program line in FIG. 2.To turn it off, NO contact S1 is reopened, and NC contact S3 is closedagain, and changeover contact S2 is switched over to its second switchcontact (switch position 1) for a time interval t1. As a result, drivemotor 13 is short-circuited via changeover contact S2 and NC contact S3,so that it comes to a standstill quickly. When the time interval t1 isover, the changeover contact S2 is switched back to its first switchcontact. All switches S1, S2 and S3 assume their home positions, whichis described in FIG. 2 as “Final State”.

[0024] If the intention is to turn on only individual fan 12, theelectronic control unit 20 triggers NO contact S1 and changeover contactS2 in such a fashion that NO contact S1 closes and changeover contact S2switches to its second switch contact, as shown in the second programline in FIG. 2. As a result, only drive motor 14 is connected to thevoltage source 17. To turn drive motor 14 back off, the two switches S1and S2 are returned to their home positions. As a result, the turned-offdrive motor 14 is short-circuited via closed NC contact S3, drive motor13, and changeover contact S2 located in switch position 0, and it isbraked to a halt very quickly.

[0025] If the intention is to put both individual fans 11, 12 intooperation simultaneously and run their electric drive motors 13, 14 in aparallel connection, then only NO contact S1 is closed, as shown in thethird program line in FIG. 2. The two drive motors 13, 14 are thereforeconnected in parallel with the voltage source 17. To turn off the twooperating drive motors 13, 14, NO contact S1 is opened, and changeovercontact S2 is switched to its second switch contact (switch position 1)for the duration t2. As a result, drive motor 13 is short-circuited viachangeover contact S2 and NC contact S3 located in its closed position,and it is braked to a halt quickly. After the time interval t2,changeover contact S2 is switched over to its “0” switch position, andits first switch contact is contacted. The slowing-down drive motor 14is therefore short-circuited via NC contact S3, drive motor 13, andchangeover contact S2, and it is braked to a halt as well.

[0026] If the intention is to put both individual fans 11, 12 intooperation, but drive motors 13, 14 must be operated in a seriesconnection, the electronic control unit 20 triggers all switches S1, S2and S3 to switch over, as shown in the fourth program line in FIG. 2. NOcontact S1 closes, changeover contact S2 is switched over to its secondswitch contact, and NC contact S3 opens. With NO contact S1 closed,drive motors 13, 14 are now connected in series with the voltage source17 via the changeover contact S2. If the operating individual fans 11,12must be turned back off, NO contact S1 and NC contact S3 are triggeredfirst of all in such a way that NO contact S1 opens, and NC contact S3closes. Drive motor 13 is therefore short-circuited via changeovercontact S2 and NC contact S3, and it quickly comes to a standstill.After a time interval t3, changeover contact S2 is triggered by thecontrol electronics 20 once more and returned to its “0” switch positionin which it contacts its first switch contact. Drive motor 14 is nowshort-circuited via NC contact S3, drive motor 13, and changeovercontact S2.

[0027] In the exemplary embodiment of the radiator blower according toFIG. 4, the radiator blower is equipped with a third individual fan 21,the electric drive motor 22 of which is connected, in a further parallelsub-circuit 23, in series with a further NC contact S3′ and a furtherchangeover contact S2′. The connection between the second switch contactof changeover contact S2 to sub-circuit 19 is broken. Instead, thesecond switch contact of the further changeover contact S2′ is connectedto the connection between NC contact S3 and drive motor 14 insub-circuit 19. The second switch contact of changeover contact S2 isconnected to the connection between the further NC contact S3′ and drivemotor 22 in sub-circuit 23.

[0028] Of course, even more parallel sub-circuits, each having a drivemotor, can be located between sub-circuits 18 and 19 in the circuitconfiguration 10 according to FIG. 4 in the same fashion as sub-circuit23. Every additional sub-circuit is designed identical to sub-circuit23. With this circuit configuration 10, all n drive motors can then beoperated individually or together in a parallel or series connection,whereby n is a whole number greater than one. When each of the operatingdrive motors is turned off, the drive motors are short-circuitedtemporarily and braked to a halt by opening NO contact S1—which iscommon to all drive motors—and correspondingly switching over NCcontacts S3, S3′ and changeover contacts S2, S2′, so that the criticalresonant frequencies of individual fans 11, 12, 21 are passed throughvery quickly.

[0029] In the exemplary embodiment of the radiator blower according toFIG. 5, the radiator blower is equipped with a total of four individualfans 11, 12, and 11′ and 12′. The two individual fans 11′, 12′—that areadditional as compared with FIG. 122—are located, with their drivemotors 13′ and 14′, in parallel sub-circuits 18′ and 19′ of the circuitconfiguration 10, whereby drive motor 14′ is connected in series with aNC contact S3″ in the same fashion as drive motor 14, and drive motor13′ is connected in series with a changeover contact S2′ in the samefashion as drive motor 13. The second active switch contact “1” of saidchangeover contact S2′ is connected to the connection between NC contactS3″ and drive motor 14′ in sub-circuit 19′. Additionally, a NC contactS3′ is installed upstream from drive motor 13′ in sub-circuit 19′. Thethree new additional switches S3′, S3″ and S2′ are triggered by theelectronic control unit 20.

[0030] In the circuit configuration shown in FIG. 5, all four drivemotors 13, 14, 13′, 14′ can be operated in parallel or individually.Moreover, drive motors 13 and 14 and drive motors 13′ and 14′ can beoperated in a series connection. Additionally, the two seriesconnections of two drive motors—13 and 14, or 13′ and 14′—can beoperated in parallel. Depending on the operating mode, the electroniccontrol unit 20 triggers the remaining switches in the necessary mannerwith NO contact S1 closed. When the operating drive motors are turnedoff, the drive motors are short-circuited temporarily and, therefore,braked to a halt, by opening NO contact S1-which is common to all drivemotors-and correspondingly switching over NC contacts S3, S3′, S3″ andchangeover contacts S2, S2′, so that the critical resonant frequenciesof the individual fans are passed through very quickly. To short-circuitthe individual motors, switches S2 and S3 must be actuated as describedfor FIG. 1, and switches S3′, S3″ and S2′ must be actuated in analogousfashion.

[0031] Additional parallel sub-circuits, each having a drive motor, canbe provided in the circuit configuration 10 according to FIG. 5 as well,whereby drive motors, NC contacts and changeover contacts areincorporated in identical fashion with parallel sub-circuits 18′ and19′. With n drive motors in n parallel sub-circuits, one changeovercontact and one NC contact are connected in series with the respectivedrive motor in the uneven-numbered sub-circuits as counted from the NOcontact S1, and only one NC contact is connected in series with therespective drive motor in each even-numbered sub-circuit. The number nof possible drive motors is an even number.

What is claimed is:
 1. A radiator blower, in particular for motorvehicles, comprising a plurality of individual fans (11, 12; 11, 12,21;11,12, 11′, 12′), each having an electrical drive motor (13, 14; 13,14,22; 13, 14,13′, 14′), and comprising a circuit configuration (10) havinga plurality of switches (S1, S2, S3; S1, S2, S3, S2′, S3′; S1, S2, S3,S2′, S3′, S3″), each of which is capable of being switched over into twopositions (0, 1), by means of which said circuit configuration the drivemotors (13, 14; 13,14, 22; 13, 14,13′, 14′) are capable of being turnedon and back off individually or in a series or parallel connection,wherein, when the operating drive motor or motors (13, 14; 13,14, 22;13, 14, 13′, 14′) is/are turned off, the switches (S1, S2, S3; S1, S2,S3, S2′, S3′; S1, S2, S3, S2′, S3′, S3″) are forced into switchpositions that bring about a short-circuiting of the turned-off drivemotor or motors (13, 14; 13, 14,22; 13, 14, 13′, 14′).
 2. The radiatorblower according to claim 1, wherein the short-circuiting of the drivemotors (13, 14; 13, 14,22; 13, 14, 13′, 14′) is brought about using onlythose switches (S1, S2, S3; S1, S2, S3, S2′, S3′; S1, S2, S3, S2′, S3′,S3″) and line connections of the circuit configuration that are providedto turn the drive motors (13, 14; 13, 14, 22; 13, 14, 13′, 14′) on andoff, and to connect them in series and in parallel.
 3. The radiatorblower according to claim 1 or 2, wherein, to turn n drive motors(13,14; 13,14,21; 13, 14,13′, 14′) on and off, they are located in nparallel sub-circuits (18, 19; 18, 19, 23; 18, 19, 18′, 19′) that areall connected to a voltage source (17) via a switch designed as an NOcontact having one active switch contact, whereby n is a whole numbergreater than one.
 4. The radiator blower according to claim 3, wherein,to operate the n drive motors (13,14; 13, 14, 22; 13, 14, 13′, 14′)individually in n−1 parallel sub-circuits (18, 19, 18, 19, 23; 18, 19,18′, 19′), one switch—designed as a NC contact (S3; S3, S3′, S3, S3′,S3″) having one active switch contact—is connected in series with eachdrive motor (13, 14; 13, 14, 21; 13,14, 13′, 14′).
 5. The radiatorblower according to claim 4, wherein, to connect the n drive motors (13,14, 22) in series in n−1 parallel sub-circuits (18, 19, 23), oneswitch—designed as a changeover contact (S2, S2′) having two activeswitch contacts—is located on the connection side of each drive motor(13, 22) opposite the NC contact (S3′, S3), the first switch contact ofwhich is located in the sub-circuit (18, 23), and the second switchcontact of which is connected to the connection between the NC contact(S3′, S3) and the drive motor (22, 14) in the subsequent sub-circuit(23, 19).
 6. The radiator blower according to claim 5, wherein only onechangeover contact (S2) is located in the first of n parallelsub-circuits (18), and only one NC contact (S3) is located in the lastof the parallel sub-circuits (19), whereby one of them is located on thehigh-potential side, and the other is located on the low-potential sideof the respectively associated drive motor (13, 14).
 7. The radiatorblower according to claim 4, wherein, for the series connection of twoof the n drive motors (13,14,13′, 14′) in each uneven-numbered, parallelsub-circuit (18, 18′) as counted from the NO contact (S1), a switchdesigned as a changeover contact (S2, S2′) having two active switchcontacts is located on the connection side of the drive motor (13, 13′)opposite the NC contact (S3, S3′, S3″), the first switch contact ofwhich said switch is located in the sub-circuit (18, 18′), and thesecond switch contact of which is connected to the connection betweenthe NC contact (S3, S3′) and the drive motor (14,14′) in the subsequent,even-numbered, parallel sub-circuit (19, 19′).
 8. The radiator bloweraccording to claim 1 or 2, wherein, when two drive motors (13,14) areinvolved, the circuit configuration (10) comprises three switches, oneof which is designed as a NO contact (S1), and another is designed as aNC contact (S3)—each having one active switch contact—and one of whichis designed as a changeover contact (S2) having two active switchcontacts, wherein the two drive motors (13,14) are located in twoparallel sub-circuits (18, 19) that are both connected to a voltagesource (17) via the NO contact (S1), wherein the NC contact (S3) isconnected in series with the one drive motor (14), and the changeovercontact (S2) is connected in series with the other drive motor (13) inone of the parallel sub-circuits (19, 18) in each case, whereby, in eachcase, one of the two switches is located on the high-potential side, andthe other is located on the low-potential side of the associated drivemotor (14, 13), and wherein, of the two switch contacts of thechangeover contact (S2), the first one is located in the sub-circuit(18), and the second one is connected to the connection between the NCcontact (S3) and the associated drive motor (14).
 9. The radiator bloweraccording to one of the claims 1-8, wherein, in order to turn the drivemotors (13,14; 13, 14, 22; 13, 13′, 14,14′) on and off, and to connectthem either in series or in parallel, an electronic control unit (20) isprovided that triggers the switches (S1, S2, S3; S1, S2, S3, S2′, S3′;S1, S2, S3, S2′, S3′, S3″) according to a specified program for changingthem over.
 10. The radiator blower according to claim 9, wherein, whenthe drive motors (13, 14; 13, 14, 22; 13, 14, 13′, 14′) are turned off,the NO contact (S1) assumes its opened position, and the NC contact (S3;S3, S3′, S3, S3′, S3″) assumes its closed position, and the changeovercontacts (S2; S2, S2′; S2, S2′) are switched over to their first switchcontacts.
 11. The radiator blower according to claim 9 or 10, wherein,when the operating drive motors (13, 14; 13, 14, 22) are turned off byopening the NO contact (S1), the NC contacts (S3; S3, S3′; S3, S3′, S3′)are changed over to their opened position, and the changeover contacts(S2; S2, S2′; S2, S2′) are temporarily switched over to their secondswitch contact.